Method of liberating and removing trapped refrigerant from the interior of an air conditioning system

ABSTRACT

A method of evacuating an automotive air conditioning system of refrigerant and recharging it with replacement refrigerant includes initially removing refrigerant from the air conditioning system, flushing the air conditioning system with hot fluid to liberate residual refrigerant from within the air conditioning system, removing the fluid and liberated refrigerant, and recharging the air conditioning system with replacement refrigerant. The hot fluid preferably is itself refrigerant in a gaseous state.

TECHNICAL FIELD

This invention relates generally to air conditioning systems, particularly automotive air conditioning systems, and more specifically to the problem of removing residual air conditioning refrigerant that is or may be trapped within oil and desiccant deposits within the system after the system is purged.

BACKGROUND

Automotive air conditioning systems are gradually getting smaller and more compact. As a result, the coolant or refrigerant charges, i.e. the manufacturer specified volume of refrigerant needed for optimum operation of the system, also are getting smaller. Further, tolerances on the required volume of refrigerant charge in the system are becoming increasingly tight. Overcharging or undercharging will result in an inoperative or reduced efficiency cooling system and can result in serious damage to air conditioning system components.

While new car air conditioning systems are properly charged with refrigerant at the factory, the tight charge tolerances often become a problem later when the air conditioning system is purged of refrigerant for service or cleaning and recharged with fresh or recycled refrigerant. More specifically, when purging and recharging an automotive air conditioning system, the old refrigerant is evacuated out of the pipes, compressor, and other components of the system by an air conditioning recycling machine for example before the system is recharged with new or recycled refrigerant. This is known as purging the system. For various reasons, not all of the refrigerant is removed during traditional evacuation. Varying amounts of refrigerant can be trapped within oil or desiccant deposits that can collect within the air conditioning system. These deposits can be very high in viscosity at normal temperatures so that the trapped refrigerant is firmly sealed therein and unable to escape during the initial purge. As a result, the trapped refrigerant remains behind and is not evacuated with the bulk of the refrigerant during the purge.

Since it is not possible to determine the volume of refrigerant that remains behind in the system, it is impossible to assure, when the system is recharged with new or recycled refrigerant, that the total volume of refrigerant (new refrigerant plus remaining non-evacuated refrigerant) is within manufacturer recommendations and tolerances. As a result, the recharging of automotive air conditioning systems has become increasingly inaccurate, particularly with smaller more compact systems. This can result in a significant over or under charge that eventually degrades system operation or causes damage to system components. Further, the residual trapped refrigerant contaminates the fresh or recycled refrigerant when the system is recharged, which can reduce the efficiency of the recharging process. In addition, standards are under development that will require that no more than three to five percent residual refrigerant remain within an automotive air conditioning system after being purged. In modem smaller air conditioning systems, this can amount to only a fraction of an ounce, an amount that easily can be trapped in the system after an initial purge.

One attempt to address the problems discussed above has been to apply a heater to external surfaces of air conditioning system components. The idea is that this externally applied heat will raise the temperature of oil and desiccant deposits inside the system and thereby liberate the refrigerant trapped therein. While this approach can be somewhat successful, it nevertheless is not a completely adequate solution. It takes time and substantial energy to heat the many components in which residual refrigerant may be trapped. Further, many of these components are buried in inaccessible locations within an engine compartment and the heating apparatus simply cannot be maneuvered in place to heat them. Further, one can never be certain precisely where all of the oil and desiccant deposits reside within the system. External heating can thus be a hit or miss proposition. As a result of these problems, trapped residual refrigerant is never completely removed with an externally applied heat approach.

Thus there is a need to be able to be able to remove virtually completely and reliably all residual refrigerant trapped within an automotive air conditioning system after an initial purge of the system, and thereby to assure that the volume of refrigerant in the system after it is recharged is precisely equal to the volume of the recharging refrigerant. It is to the provision of a novel method of addressing this need that the present invention is primarily directed.

SUMMARY OF THE INVENTION

Briefly described, the present invention is a method of purging an automotive air conditioning system of substantially all refrigerant, including substantially all refrigerant trapped in oil, desiccant, or other deposits within the system, before the system is recharged. The method comprises the steps of initially evacuating the system of refrigerant in a traditional manner. After the initial evacuation, the air conditioning system is flooded or flushed with a high temperature fluid, which preferably is heated refrigerant in a gaseous state. The high temperature refrigerant permeates the entire air conditioning system to contact and heat any deposits within which residual refrigerant may be trapped, thus heating the deposits and the trapped refrigerant therein. The temperature of the refrigerant is sufficiently high and the duration of the flush sufficiently long to insure that the deposits are heated to a temperature sufficient to liberate refrigerant trapped therein. The liberated refrigerant then simply mixes with the high temperature refrigerant used for the flush, and the system is again evacuated to remove all of the flushing refrigerant and the previously trapped refrigerant entrained therein. Thereafter, the system can be recharged with fresh or recycled refrigerant, with the total volume of the charge being equal precisely to the volume of the recharging refrigerant. In this way, the charge is precisely measured and determined to comply with manufacturer recommendations and tolerances.

Thus, a novel method is now provided that addresses the problems and shortcomings discussed above. The method will be better understood upon review of the following detailed description of the preferred embodiment, and best mode known to the inventor, for carrying out the invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

The present invention comprises a method of evacuating and recharging an automotive air conditioning system that removes virtually all trapped refrigerant and assures an exceedingly accurate refrigerant charge volume following the process. The method can be carried out with any of a number of commercial air conditioning refrigerant recycling machines such as, for example, the model MAC-34AE available from Manatec Electronics of Pondicherry, Ind. The method includes first connecting a refrigerant recycling machine to the charging ports of the air conditioning system in the traditional manner. The machine is then operated in its evacuation mode to effect an initial evacuation of refrigerant from the air conditioning system.

After the initial evacuation phase, residual refrigerant remains trapped within oil and desiccant deposits inside the system. To liberate and remove this trapped refrigerant, the recycling machine is operated again in its recharging mode, except that, instead of supplying recharging refrigerant to the system, the recycling machine injects and flushes through the system a stream of refrigerant that has been heated to a relatively high temperature and that preferably is in a gaseous state. Any appropriate mechanism for heating the refrigerant can be used, such as, for example, an electric heating element surrounding the outlet line of the recycling machine. Alternatively, an independent supply of heated refrigerant from a separate pump or other source can be used. Regardless of the heating mechanism, the refrigerant should be heated to a temperature of at least 200 degrees Fahrenheit and preferably to a temperature of at least 400 degrees Fahrenheit or higher before it is injected into the air conditioning system.

As the heated refrigerant is injected into and floods through the interior of all components of the air conditioning system, it comes into contact with any oil, desiccant, or other deposits that may have collected anywhere within in the system. This causes the deposits, and the surrounding internal components of the system, to be heated. As the deposits heat up, their viscosity is reduced significantly to perhaps one fifth or less of the viscosity they exhibit at ambient temperatures. Further, residual refrigerant trapped within these deposits also is heated so that, if not already in a gaseous state, it evaporates energetically within the deposits. The combination of the energetic evaporated refrigerant and the substantially less viscous deposits allows the trapped refrigerant to escape easily from the deposits. The escaped refrigerant, then, mixes with and becomes entrained within the gaseous refrigerant used to flush the system.

When a sufficient time as passed to insure that substantially all of the trapped refrigerant has been liberated as described above, the air conditioning system is again evacuated with the recycling machine in its evacuation mode. The amount of time during which the hot refrigerant must remain in the system can vary as a function, for instance, of the ambient temperature, the initial temperature of the air conditioning system components, and/or the temperature to which the gaseous refrigerant is heated prior to being injected into the system. The goal is to allow the hot refrigerant to flow through the system for a time period sufficient for all internal oil, desiccant, and other deposits and surrounding structures to be heated to a temperature high enough to allow the trapped refrigerant therein to evaporate and escape. It is believed that where the flushing refrigerant is heated to a temperature of about 400 degrees Fahrenheit prior to being flushed through the system, and the ambient temperature and temperature of the air conditioning system components is about 70 degrees Fahrenheit, the hot refrigerant should flow through the system for at least 10 seconds and perhaps up to several minutes. One indicator may be that when the temperature of the refrigerant exiting the system approaches that of the hot refrigerant being injected, then a sufficient time has passed.

After the second evacuation of the system to remove the heated refrigerant and the previously trapped refrigerant entrained therein, the air conditioning system is in a purged state with virtually no remaining refrigerant trapped therein. The system can then be recharged with fresh or recycled refrigerant in the traditional manner using the recycling machine in its recharge mode. The volume of refrigerant with which the system is recharged can be measured very accurately by modern air conditioning recycling machines during the recharging phase so that it is well within the tight tolerances for the air conditioning system. Since there is virtually no remaining residual refrigerant in the system, the final charge volume is essentially equal to this accurately measured recharge volume. Consequently, an overcharged condition, which can occur with prior art methods, is virtually eliminated. Undercharging also can result with prior art methods when a “guess” is made as to how much residual trapped refrigerant may be in the system and the volume of recharging refrigerant adjusted to compensate. With the method of this invention, however, undercharging also is virtually eliminated because no compensation for trapped residual refrigerant is necessary.

In addition to insuring a proper charge, the method of the present invention also virtually eliminates the problems associated with contamination caused by residual refrigerant within an air conditioning system. Further, any new standards regarding the amount of allowed residual refrigerant following a system purge are met easily and with confidence using the method of the present invention.

The invention has been described herein in terms of preferred embodiments and methodologies that represent the best mode known to the inventor of carrying out the invention. Various modifications to the preferred methodology are possible within the scope of the invention. For example, the preferred methodology is for use with an automotive air conditioning system. However, the invention is not limited to automotive systems but is also applicable to other cooling systems such as residential or commercial air conditioning systems or even the cooling systems of refrigeration equipment. Further, the preferred methodology involves the use of an air conditioning recycling machine. The invention is not limited to such recycling machines but might be carried out using various mechanisms and systems for purging and/or recharging air conditioning systems. The temperature ranges and time periods described above should not be considered essential or limiting. Any combination of temperatures and times sufficient to cause the liberation of trapped refrigerant are acceptable and all should be considered to be within the scope of the invention. Finally, in the preferred embodiment, heated refrigerant is the fluid used to flush the air conditioning system and liberate trapped refrigerant. While this is preferred for at least the reason that the liberated refrigerant mixes easily with the flushing refrigerant, the invention is not so limited. Any fluid appropriate for the function of flushing the system as described herein, be it in a liquid state or a gaseous state, is contemplated and within the scope of the invention. These and other additions, deletions, and modifications might be made by those skilled in the art without departing from the spirit and scope of the invention as set forth in the claims. 

1. A method of evacuating refrigerant from an air conditioning system and recharging the air conditioning system with replacement refrigerant, the method comprising the steps of: (a) evacuating refrigerant from the air conditioning system; (b) flushing the air conditioning system with a heated fluid to liberate residual refrigerant from within the system; (c) evacuating the heated fluid and liberated refrigerant from the air conditioning system; and (d) recharging the air conditioning system with replacement refrigerant.
 2. A method of evacuating refrigerant from an air conditioning system and recharging the air conditioning system with replacement refrigerant as claimed in claim 1 and where in step (b) the refrigerant is heated to 200 degrees Fahrenheit or greater.
 3. A method of evacuating refrigerant from an air conditioning system and recharging the air conditioning system with replacement refrigerant as claimed in claim 2 and where in step (b) the refrigerant is heated to 400 degrees Fahrenheit or greater.
 4. A method of evacuating refrigerant from an air conditioning system and recharging the air conditioning system with replacement refrigerant as claimed in claim 1 and where in step (b) the air conditioning system is flushed with heated fluid for at least 10 seconds.
 5. A method of evacuating refrigerant from an air conditioning system and recharging the air conditioning system with replacement refrigerant as claimed in claim 4 and where in step (b) the air conditioning system is flushed with heated fluid for at least three minutes.
 6. A method of evacuating refrigerant from an air conditioning system and recharging the air conditioning system with replacement refrigerant as claimed in claim 1 and where in step (b) the heated fluid is heated refrigerant.
 7. A method of evacuating refrigerant from an air conditioning system and recharging the air conditioning system with replacement refrigerant as claimed in claim 6 and wherein the heated refrigerant is in a gaseous state.
 8. A method of evacuating refrigerant from an air conditioning system and recharging the air conditioning system with replacement refrigerant as claimed in claim 1 and where in step (b) the heated fluid is in a gaseous state.
 9. A method of removing residual refrigerant from an air conditioning system after the air conditioning system has been initially purged of refrigerant, the method comprising heating a flushing fluid to a predetermined temperature, injecting the flushing fluid into the air conditioning system, leaving the flushing fluid in the air conditioning system for a predetermined time to heat and liberate residual refrigerant therein, and removing the flushing fluid and liberated refrigerant from the air conditioning system.
 10. The method of claim 9 and wherein the heating step comprises heating the flushing fluid to at least 200 degrees Fahrenheit.
 11. The method of claim 9 and wherein the heating step comprises heating the flushing fluid to at least 400 degrees Fahrenheit.
 12. The method of claim 9 and wherein the leaving step comprises leaving the flushing fluid in the air conditioning system for at least 10 seconds.
 13. The method of claim 9 and wherein the flushing fluid is refrigerant.
 14. The method of claim 9 and wherein the air conditioning system is an automotive air conditioning system.
 15. A method of removing residual refrigerant from an air conditioning system comprising heating a flushing fluid to a predetermined temperature, flushing the air conditioning system with the flushing fluid for a predetermined time to liberate residual refrigerant; and evacuating the flushing fluid and liberated refrigerant from the air conditioning system. 